Hot water from a boiler or hot water heater is the medium for heat transfer in a hydronic
system. Radiators are the most common source of heat transfer, but radiant loops are gaining
popularity. Installation and materials costs have made aluminum finned copper tubing the
most effective style. Once the heat loss of a room has been determined, a measured length
of baseboard (low output or high output) or the correct size free standing cast radiator
can be installed. Baseboard, whether copper or cast iron, is run in a continuous loop from
room to room, but the

larger cast standing radiators work better as a supply and return
loop or as a monoflo loop. Using a fitting called a monoflo T, One pipe can feed the entire
loop of standing radiators. Unique but simple, the monoflo T uses an orifice placed to one
side of the t arm to restrict the flow of water through it. Down side of the flow it forces
water into the arm. Upside of the flow and suction is produced. Water is forced in and out
of the radiator without valves or a separate pump.

Using
the concept of warm feet as an important comfort factor, radiant heating is becoming more
popular, but continues to be more expensive to purchase and install. It can be stapled to
the underside of the sub-floor, embedded in a concrete slab, or strung between the ceiling
joist to radiate down from the ceiling for double the pleasure or when refitting a room
with an existing slab floor. When embedded in a concrete slab, response time is slow and
gradual, so the water must circulate constantly and the thermostat set at the desired temperature
and left alone.